The invention relates to a light-mixing rod for homogenizing a light bundle, preferably for use in projection devices, wherein the intensity centroid of the light bundle moves in a longitudinal direction between a light inlet surface and a light outlet surface, and reflecting surfaces are present in the light-mixing rod, the surface normals of said reflecting surfaces being perpendicular or inclined relative to said longitudinal direction, with partial beams being reflected by said reflecting surfaces for the purpose of guiding the light bundle.
In the optical field, light-mixing rods (integrators) are used, in particular, where uniform illumination of fields of illumination is required. Embodiments thereof are solid mixing rods (utilizing the total reflection at the interfaces to the air) or hollow mixing rods, which essentially consist of a basic body whose lateral surfaces are uniformly provided with reflecting coatings. Light coupled into the integrator via the light inlet surface is reflected back and forth several times at the reflecting surfaces until it reaches the light outlet surface. On account of the so-called “mixing” of the light, a homogenized field of illumination is formed on the light outlet surface, depending on the cross-section and the length of the integrator. A solution of this kind is described, for example, in DE 198 19 245 C1.
One possibility of generating a uniformly illuminated field in the light outlet surface is to, first, image the field of illumination of a burner arranged in the primary focus of an ellipsoid reflector into the secondary focus of said ellipsoid reflector. This field of illumination is very inhomogeneous and has an aperture which depends on the angular radiation characteristic of the burner and on the opening of the ellipsoid reflector. The inlet surface of the light-mixing rod is illuminated using this spot of the secondary focus. If the lateral surfaces of the integrators are parallel to each other, the apertures in the light outlet surface correspond to the apertures in the light inlet surface.
Such variants are very complicated in structural terms. On top of this, there is the relatively great complexity of adjustment for coupling the light bundle into the light-mixing rod. For example, in order to realize a color management having a variable adjustment of color, additional, mechanically moved parts are required.
In view of the disadvantages of the described prior art, it is an object of particular embodiments of the invention to conceive a light-mixing rod reducing the structural complexity required to produce a homogenized field of illumination and allowing a variable color adjustment of the field of illumination without additional, mechanically moved structural components.